Choke for controlling the flow of drilling mud

Abstract

This apparatus disclosed in its preferred form is a choke for controlling the flow of drilling mud which is highly abrasive. The abrasive drilling mud is introduced through a lateral port and an elongate, tubular body. In the tubular body, a fluid actuated, double acting piston is forced to a choke control position. The piston has appended to it a centralized, tubular extension which receives a sleeve of wear resistant material. The sleeve is positioned in a circular chamber communicated to the lateral port where the drilling mud is introduced. It travels toward a seat downstream of the body. The seat is formed of hardened material. The downstream outlet of the body is additionally lined with a wear resistant sleeve. An alternate embodiment is also disclosed. A hydraulic control system for operation of the choke is also disclosed.

I claim: 
     
       1. A choke for controlling the flow of mud which comprises: a hollow valve body having a passage therethrough;   a valve seat having an encircling, tapered face surrounding an axial passage past said tapered face for directing mud flow past said tapered face within said valve body;   an encircling valve seat shoulder axially spaced from said tapered face lying in a plane perpendicular to the flow through said axial passage;   a valve element having an external tapered face conforming to said valve seat tapered face which said valve element, on movement, moves from a spaced position into a concentric, centrally positioned first throttling location within said valve opposite said valve seat tapered face and which said valve element and said valve seat tapered faces define a gap therebetween for throttling mud flow passing through the gap, and wherein said valve element controllably blocks the axial passage flow of mud past said valve seat on further movement of said valve element toward said valve seat shoulder defining a second throttling location having reduced flow compared to said first throttling location;   a surrounding shoulder on said valve element which shoulder is adapted to conform to and seat against said valve seat shoulder to plug and close the flow of mud through the gap between said valve element and said valve seat, said shoulder further moving toward said valve seat shoulder for closure;   means for moving said valve element into a fully closed position relative to said valve seat; and   inlet and outlet means communicating with said passage through said valve body.   
     
     
       2. The apparatus of claim 1 including a piston having a protruding end portion equipped with a detachable means for mounting said valve therein for axial telescoping movement into and out of engagement with said valve seat. 
     
     
       3. The apparatus of claim 2 including a cylinder surrounding said piston and aligning it for sealing movement into and out of contact with said valve seat. 
     
     
       4. The apparatus of claim 3 including a hollow body having an axial passage for receiving and supporting said valve seat therein. 
     
     
       5. The apparatus of claim 4 including a port opening into said hollow body introducing a flow of fluid toward said valve seat and a second port downstream from said valve seat which serves as an outlet. 
     
     
       6. The apparatus of claim 4 including an elongate body of circular cross section which terminates in an end portion serving as said valve element and which body is mounted on said piston, said piston incorporating a bolt means centered therein which removable bolt clamps said valve body in place. 
     
     
       7. The apparatus of claim 6 including lock means which clamps said valve seat into a fixed position relative to said valve element, said lock means comprising a latch means for an elongate, hollow sleeve comprising said valve seat. 
     
     
       8. The apparatus of claim 7 wherein said sleeve is double-ended and duplicated at both ends, each end including said valve seat and being reversible to enable said sleeve to be repositioned and thereby allowing use of both ends. 
     
     
       9. The apparatus of claim 8 wherein said valve element is a portion of a removable part which is provided with duplicate ends and is reversibly received in said choke to enable both ends to function as a valve element. 
     
     
       10. The apparatus of claim 1 wherein said valve seat and said valve element include concentric, cylindrical surfaces spaced apart by a specified distance such that said valve element fits within said valve seat with clearance defined by the specified distance.